Sanboji in Settsu Nakajima is a temple built by Nonin in order to spread the Dharma sect. This article traces the origin of the temple by referring to literature of the Middle Ages and old maps.Recently, the origin of the Sanboji temple has been traced to Daido-the second and third wards of the neighborhood of the Osaka University of Economics in Daido district. However, topography and medieval documents connected with the Sozenji, Monoi family, and so on, suggest that the origin of the temple is not restricted to Daido, but extends to the wider-ranging area of Komatsu Zuiko and Osumi district, spanning the whole territory. Although the time of existence of the temple is still unknown, it is believed to have existed until the third year of Onin (1469), based on the “_??__??__??__??__??__??__??__??__??__??__??__??__??__??__??__??__??__??_” of the Shoboji historical records. Furthermore, its existence during the time of Daiei (1521-1526) or Kyoroku (1528-1531) is questioned. Even though the temple disappeared, the Komatsu and Nishidaido districts located to the north from the origin of Sanboji were called Sanboji, and remained so until the first half of the 20th century.